DSpace Collection: Ph.D Theses

MECHANICAL PROPERTIES AND MACHINABILITY EVALUATION OF ANNEALED TITANIUM GRADE 2

2025-09-04T00:39:30Z

Title: MECHANICAL PROPERTIES AND MACHINABILITY EVALUATION OF ANNEALED TITANIUM GRADE 2 Authors: LOUIS DENIS KEVIN CATHERINE, UniKL MIDI Abstract: The rapid growth in the utilization of titanium has brought many manufacturing challenges. Developing a new sustainable machining strategy is of utmost importance. In this study, the machinability of commercially pure titanium grade 2 (CP-Ti grade 2) was investigated under three different conditions of CP-Ti grade 2 namely, as-received (T1), annealed at 700°C (T2) and 900°C (T3). The response were cutting force, cutting power and surface roughness. The data collected from the tensile test indicate that there was an increase in ductility in T2 compared to T1 and T3 workpieces but T2 demonstrates a decrease in tensile strength. The XRD (X-Ray diffraction) analysis on the developed oxidation layer showed that T2 had a thin oxidation layer of 843 nm whereas T3 had a thicker layer of 20 μm. The formation of the oxide layer on CP Ti grade 2 is beneficial to the biomedical implants for the proper cell attachment. A full factorial design of experiment (DOE) was applied with three factors at two levels and three replicates. The machining parameters used during this study were cutting speed at 110 and 130 m/min, depth-of-cut of 0.1 and 0.3 mm and feed rate of 0.12 and 0.35 mm/tooth. Due to the decrease in hardness of T2, the cutting forces recorded was 30 % lower compared to the T1 and T3. On the other hand, the average cutting power was also found to be lower by 15 % during the milling operation of CP-Ti grade 2. The evaluation of the surface roughness under the minimum quantity lubrication (MQL) with the newly adjustable nozzle system demonstrates that low surface roughness of 0.2 μm can be achieved rather than under dry or flood condition. Finally, this study found that by annealing CP-Ti grade 2 at 700°C for one hour can contribute to a better machinability due to a soften effect that reflected on the hardness value of 180 Hv under an MQL condition. It was also found that the optimum milling parameter was with a cutting speed of 130 mm/min, feed rate 0.12 mm/tooth and depth of cut of 0.1 mm that can achieve the lowest cutting power and cutting force. This valuable data can contribute to the industry so that the machinability of CP Ti grade 2 or similar material with the same range of hardness can be machined without much difficulty.

RATIONAL DECISION MODEL FOR SELECTION OF IMPROVEMENT INITIATIVE USING EXPERT MAPPING STUDY

2025-09-03T01:44:19Z

Title: RATIONAL DECISION MODEL FOR SELECTION OF IMPROVEMENT INITIATIVE USING EXPERT MAPPING STUDY Authors: MOHAMAD IKBAR BIN ABDUL WAHAB, UniKL MIDI Abstract: The rapid interest growth for the adoption of Improvement Initiative (IMI) indicates the importance of improvement to sustain the business and to remain competitive. This phenomenon contributes to the extensive evolution of IMI introduced throughout the recent decades compared to its initial introduction. However, the existence of a bundle of IMI has caused difficulties to organizations to select the most suitable improvement initiative to be adopted. In addition, the failure in the deployment of IMI in numerous organizations has been frequently reported to be associated with a poor selection. In the absence of explicit key decision criteria, decision makers highly depend on subjective judgements which are biased to the experience and which tend to follow the fashion setting. This study aimed to fill the research gap by proposing the rational selection for IMI adoption based on the phenomena and developing a theory of selection by bringing all influential criteria together in one comprehensive model. This study incorporated cross-paradigm (Constructivism & Positivism) as a research paradigm and adopted a mix method research, including quantitative and qualitative to meet its objective. Based on rigorous systematic literature review (SLR) steps, a total of 164 publications were used to extract and synthesize the information. The information from the SLR enables the development of an empirical model for the selection of IMI through the provision of wide angles selection criteria which provide holistic decision supports for decision makers. The quantitative research approach was adopted to ensure generalization of the model, highlighted as limitations by previous researchers with a total of 241 respondents’ feedback from various organizations. The reflective-formative hierarchical model was analyze using structural equation modelling through Smart PLS software in order to develop rational selection model for IMI. Upon validation of the model, six selection views with 33 attributes were decided to be considered by decision makers prior making decisions on the most suitable IMI to be adopted in their organizations. The development of intelligent decision support system for IMI selection was derived from the mapping of IMI with selection criteria based on experience and knowledge of experts. The functionality of the system was tested through Black Box Testing prior measuring the practicality of the system to help the decision makers by using a structured case study protocol. The results from Kendal Coefficient of Concordance analysis indicate that, the system is able to perform well to help decision makers to select the most suitable IMI to be implemented in their organizations. As a conclusion, this empirical study provides rational decision making for the selection of IMI by providing wide angle selection criteria which avoid subjective judgements which could lead to the failure of improvement in the organizations. The rational selection model enables organizations to manage and carefully select improvement initiatives to ensure effectiveness of the selection and a successful implementation of IMI.

AN INTEGRATED OPTIMIZATION METHODOLOGY OF THE ELECTRICAL DISCHARGE MACHINING USING BOX BEHNKEN METHOD AND GENETIC AlGORITHMS

2025-09-03T01:35:26Z

Title: AN INTEGRATED OPTIMIZATION METHODOLOGY OF THE ELECTRICAL DISCHARGE MACHINING USING BOX BEHNKEN METHOD AND GENETIC AlGORITHMS Authors: IMAD MOKHTAR A. MOSRATI, UniKL MIDI Abstract: Products used in critical industries like aerospace, automotive and power plant require specific and critical limits of the material properties. In aircraft a slight deviation from required specifications may result in the loss of both lives and equipment’s. Due to advancement in the industry, special material is used, therefore continuous study is required to optimize the properties of these materials. Nickel Chrome Alloy Steel and Powdered Metallurgical High-Speed Steel Alloy are important materials in industries, these alloys are used in different industries like automotive, aerospace, and electrical station industries, they are used in applications such as resistors, gears, shafts, tools. These component materials fail in the industry due to the high utilization rate and due to the lack of required specifications that are affected during the manufacturing process. Through the EDM manufacturing process, the temperature is very high, product properties and microstructure affected, the huge temperature in EDM lead to the material phase transformation, affect material properties, and surface defects are generated, and may cause the product to fail in the industry. Another issue, the post-treatment process should be performed after the manufacturing process, to restore the microstructure and to improve material properties, which costs a lot of money. In this research, two types of electrodes are used, silver-tungsten and copper-tungsten to optimize the EDM performance. The optimum combinations of the input parameters are important, which affects the EDM responses and material surface properties. In this study, an investigation of the effect of a new input parameter called pulse cycle time (Tc), in addition to dielectric liquid pressure (P), Voltage (V), and electrode material on the EDM responses was done. Box Behnken design methodology and Genetic Algorithm (GA) optimization methodology are used as an integrated approach to model and optimize the electrical discharge process. Two softwares, Minitab and Matlab are utilized for this purpose. Outputs are Machining Time (MT), Material Removal Rate (MRR), Tool Wear Rate (TWR), Over Cut (OC), Surface Roughness (SR), Hardness, Micro crack width (MCW), and Recast Layer thickness (RLT). 3D Laser Microscope is used to measure and inspect the surface defects. An interface expert system was built and used as a response predictive tool and used as a historical database. Based on result analysis and ANOVA tables, it is concluded that (Tc) as investigated new input parameter is significant, because its effect probability (p-value) is less than 0.05 for the most responses. From the results of Genetic Algorithm optimization, for the material Nickle Chrome Alloy Steel, it is concluded that the copper-tungsten electrode is the best for minimum MT, TWR, SR, MCS, RLT, and maximum MRR. While the silver-tungsten is the best for the minimum OC, and maximum Hardness, so the tool material is a significant parameter. The integrated methodology used in this study has proven as an effective tool, where the values of some outputs are improved up to 68.42% better than experimental values.

SYSTEMATIC MECHANICAL PERFORMANCE STUDY FOR SILICON CHIP IN ELECTRONIC PACKAGING USING UNIFIED APPROACH

2025-08-20T05:26:43Z

Title: SYSTEMATIC MECHANICAL PERFORMANCE STUDY FOR SILICON CHIP IN ELECTRONIC PACKAGING USING UNIFIED APPROACH Authors: WONG SHAW FONG, UniKL MIDI Abstract: Ultra-thin chip technology has the potential as the possible solution on overcoming the bottlenecks in silicon technology for new miniaturized applications. However, it increases the potential mechanical risk with such ultra-thin silicon chip solution and requires a comprehensive understanding to appropriately characterize its mechanical integrity and fracture. Hence, the lack of a full structural study from initial silicon chip break strength (SBS) study, to the interaction impact from assembly processes on a final assembled thin packages' silicon chip stress has been identified as the opportunity on this research work. A four stages unified approach for potential silicon chip cracking risk quantification is proposed. First, a simple and practical experimental three pint bend (3PB) SBS investigation with beam theory was initially carried out to study the key silicon process parameters without a need to undergo a complex and heavy computational analysis. Simultaneously, a useful stress-based modeling approach on those critical factors as identified in design, test process and reliability were carried out to analyze and predict the silicon surface stress parametrically. Then, a practical application integrating both experiment and modeling through a universal defect metric with bending stress, namely is established. The realistic risk analysis on those identified electronic packaging (EP) design options and test interaction could be easily predicted, although the preliminary assessment showed an approximately 40% of survival margin for an ideal conditions initially. However, with further inclusion of the critical safety factors, combining the laser marked SBS and higher chip surface stress build up in reliability test, the margin was reduced to <5%, which revealed the significance of this newly developed unified approach in predicting the realistic mechanical assessment for the EP's silicon chip. Besides, a further study was extended to explore a potential and cost effective SBS enhancement option with surface protection opportunity, which improved the SBS by approximately 33%, and validated to be transparent to existing process flow. Through the few test cases with unified approach, it was also suggested that a better EP stiffness control along with a surface protection like the overmold (OM) EP solution was needed for better ultra-thin chip performance enhancement. The completion of this research produced a good benchmark on the effectiveness of systematic unified approach to quantify the ultra-thin silicon chip cracking risk. This unified assessment with a well-structured four phases of research study drives for a potential optimization in design, material and process selection, as well as enhancement opportunity to improve the EP's silicon chip mechanical performance. This approach enables a quick and direct risk level assessment on various critical factors for potential silicon chip cracking failure avoidance.